The present disclosure relates to an air filter for forced air heating, ventilating and/or air conditioning (“HVAC”) systems. More specifically, the present disclosure relates to an air filter having a plurality of flat pleats which facilitates better bonding with a reinforcing structure and strengthens the filter media such that the surface area of the filter media is greater and the pressure drop of the air moving through the air filter is lower than conventional air filters.
Pleated paper filter elements of the type used in forced air systems require replacement when filter surfaces become so covered by dust and dirt particles that they clog the paper filter, that they restrict air flow. For a required air flow rate and filtration, the useful life of the filter or the time between cleaning depends on its surface area. Thus, to increase the useful life of a filter element, the surface areas typically increase.
One method to increase filter surface area is to increase the size the of the pleated filter, the depth of the pleats or the pleat density. In many HVAC systems, the height and width dimensions of a pleated filter usually cannot be increased due to physical constraints of the forced air system. Accordingly, reasonable methods to increase the surface area are limited to increasing the depth of the pleats and the pleat density. However, the surface area of the filter media is also a major factor in determining flow resistance (i.e., pressure drop) and loading capacity of the pleated filter.
The ability of an air filter media to withstand operating pressures is typically dependent upon the pleat count, the pleat depth and the stiffness of the filter media. The filter media can become unsteady when air pressure is applied to one side. In the event the pleats deform or collapse, a portion of the surface area can be reduced and the pressure drop or across filter element will increase, further increasing the force applied to the filter media.
For example, in one prior art design an accordion folded filter element includes planar reinforcing strips bonded to pleat tips by an adhesive. Another prior art design utilizes a glue bead applied prior to folding of the filter media which connects the folds with one another at the point of application. Yet another prior art design spaces the folds of the pleated filter media using a tapered assembly comb having uniformly spaced teeth. Still another prior art design utilizes a truss-type of reinforcing structure.
Therefore, there is a need for an air filter that provides more filter filter media area, reduces pressure drop, provides better bonding between the filter media and a reinforcing structure, has more uniform pleats, aids in the processing of the filter media and decreases material and manufacturing costs.